The security of home entrances is becoming increasingly important with break-in attempts on the rise. A number of different suggestions have already been made with a view to increasing the security of home entrances having roll-up blinds or doors.
DE-PS 30 19 566 and DE-OS 25 21 183 propose that the lowest slat be fitted with laterally-slidable locking bolts that interact with a spring the force of which presses such bolts into a specially provided bolt recess whenever, during closing of the roll-up blind or door, the force that pulls against the spring tension is absent. The force is transmitted by a cable that connects the uppermost securing bolt to the bolt provided in the lowest slat. This arrangement makes use of the fact that, during opening and closing, the space separating the slats of a roll-up blind, gate or door will be greater than that separating the slats when the roll-up blind, gate or door is closed. This difference is transmitted to the locking bolt via a traction cable that runs from one of the upper slats to the last, lowermost slat.
During opening and closing, the locking bolt is retracted by means of the traction cable. When the blind is in the closed position, where due to the narrower gap between the slats, the traction cable is relaxed, the securing bolt is slid outwards under spring tension into the lateral recesses. If at this point an upper slat is lifted up during a break-in attempt, the slats are further separated from each other, which causes the traction cable to tighten, which in turn causes the securing bolt to retract, the result being that the roll-up blind, gate or door can now be opened by pushing up from the bottom.
The disadvantage of this arrangement is that the locking action depends on the reduction in cable tension; however, the cable tension remains the same, if for instance, the cable jams, which would prevent locking. Alternatively, should the spring break, the locking bolt could be forced into the locking position, a condition that will not always be noticed, particularly if the roll-up blind, gate or door is controlled automatically by means of timer or light switches. Furthermore, and particularly wherever varying widths of roll-up blinds or doors are available, a single or double-sided securing system is no longer considered to be adequate. Rather, there is a need for securing devices that lock at several points.